/Engine/Source/Editor/UnrealEd/Public/PackageTools.h
Tries to convert a given relative or absolute filename to a long package name or path starting with a root like /Game This works on both package names and directories, and it does not validate that it actually exists on disk.
Resulting long package name if the supplied filename properly maps to a long package root, empty string otherwise.
static [FString](API\Runtime\Core\Containers\FString) FilenameToPackageName ( const [FString](API\Runtime\Core\Containers\FString) & Filename )